EFFECT OF VARIOUS SEED MATERIALS ON THE RATE OF PRECIPITATION OF SODIUM JAROSITE AND AMMONIUM JAROSITE

摘要

The beneficial effect of sodium jarosite seed on the rate of precipitation of sodium jarosite at 98℃rnwas confirmed, and the initial rate of precipitation increased linearly with the amount of jarosite seedrnpresent. Zinc plant hot acid leach residue, which contained a major fraction of sodium jarosite, was almostrnas effective as sodium jarosite seed itself. Lead sulphate, which may react superficially to form leadrnjarosite, also had a significant positive effect on the rate of sodium jarosite precipitation. The presence of arnnumber of other materials, including zinc plant manganese cell sludge, zinc ferrite, gypsum, anhydrite andrnquartz, had a positive effect on the rate of precipitation of sodium jarosite and ammonium jarosite.rnHowever, these materials were less effective than jarosite seed additions for accelerating the rate ofrnprecipitation of jarosite-type compounds. Mineralogical examination of the precipitates made in thernpresence of the above seed materials consistently found that the jarosite precipitated preferentially on, andrnrimmed, the seed particles. In contrast, additions of hematite, elemental sulphur and Pyrex glass had littlerneffect on the rate of jarosite precipitation. Mineralogical study of these latter precipitates revealedrnintergrown masses of jarosite with the seed material but little systematic rimming of the seed particles. Allrnmaterials wetted by the synthesis solution seemed to promote the rate of precipitation of jarosite-typerncompounds, but some of the materials were more effective than others.